PCI for Acute Myocardial Infarction Caused by Left Main Disease

Percutaneous revascularization of left main coronary lesions is a hot topic. During the recent TCT conference, multiple live cases and discussions were dedicated to new advancements in the treatment of left main disease. The high level of interest stems from recognition of the tremendous contribution of drug-eluting stents to successful long-term treatment of atherosclerotic coronary disease and from a prevailing feeling among interventionalists that with recent improvements of other types of equipment the field is ready to approach the “last frontier.” Left main coronary disease is a rare angiographic finding.¹ Patients with severe obstructive disease of the left main artery can present with stable or unstable angina or with an acute evolving myocardial infarction.² Collaterals from the right coronary artery may be present but their existence is not a guarantee that acute myocardial infarction cannot occur.³ For the interventionalist the care of an AMI patient with left main disease presents a difficult challenge and an unmatched level of urgency or emergency. This is due to the devastating combination of an unforgiving anatomical location with the immense extent of under perfused myocardium which is rapidly undergoing relentless ischemic changes and irreversible destruction and necrosis.⁴ In this issue, Sakai and colleagues⁵ present their cumulative clinical experience with AMI associated with left main disease. Over a period spanning 9 years (1992–2000) they treated 1,736 consecutive patients with AMI (average of 16 patients per month) who underwent emergent cardiac catheterization within 12 hours of symptom onset. Of these patients, 38 (2.2%) who had left main stenosis and exhibited reduced TIMI flow received emergency primary angioplasty. The authors noted that most patients (74%) presented to the cardiac catheterization suite in cardiogenic shock. The authors are to be commended for their dedication and commitment to treat their patients. However, overall, only 45% of the entire series survived. This disappointing outcome should be viewed within the correct context of an unusual critical clinical condition. Simply stating, every single patient treated by Sakai et al. would have been excluded from almost any AMI study because of the a priori unacceptable high risk for PCI. Analyzing the data, Sakai and colleagues identified a survival group that included patients with an improved physiologic, metabolic and hemodynamic condition upon presentation to the cath lab. Specifically, those with cardiogenic shock had a considerably lower success rate of angioplasty (68%) versus those with preserved left ventricular ejection fraction. Importantly, there was no difference in the rate of stenting between patients with cardiogenic shock versus those without shock. Since angioplasty is the most expedient revascularization method for AMI it was attempted, however, failed angioplasty practically meant demise of the treated patient in the series of Sakai et al. A question then arises, as to whether presently there is a chance to improve results in this devastating clinical situation or wheter we should accept the inevitable destruction of myocardium and failure of reperfusion. The key to the answer and for improvement of perfusion and success in this situation can be found, in my opinion, in one sentence within the discussion section of the paper: “A relatively large amount of angiographically visually thrombus was shown in all LMCA lesions.” Focusing on this provides a potential for different revascularization approach. Today’s contemporary treatment calls for specific antithrombotic strategy. While the authors treated their patients with standard heparin therapy, it is plausible that mechanical thrombectomy devices could have provided better yield in the presence of visible thrombus.^6,7 A growing recent experience with such modalities for AMI denotes to the remarkable efficiency and safety of thrombectomy devices such as X-Sizer⁸ and excimer laser.⁹ Furthermore, nowadays we recommend the administration of Bivalirudin¹⁰ as it can enhance the yield of any thrombectomy device. At the present, the interventional field is moving toward a consensus that lesions located either at the ostium or middle portion of the left main artery can be approached successfully with percutaneous techniques providing that the operator is considerably experienced and technically savvy with high risk PCIs. In cases of distal lesion of the left main artery, bypass surgery is probably still the best treatment option for stable patients due to the considerably difficulties in stenting of a bifurcation lesion located at such a critical anatomically location. This approach will remain valid until a dedicated bifurcational stent will become available. Admittedly, in the context of an evolving AMI, especially in hemodynamically unstable patients such as in the Sakai et al. series, the above-mentioned surgical option needs to be evaluated and at times deferred to PCI. Revascularization of the left main in the presence of AMI will remain a formidable challenge for a long time.

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